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# callAsFunction(at:)

Opens the document at the specified file URL.

```
@MainActor func callAsFunction(at url: URL) async throws
```

## Parameters

`url`

A file URL that points at an existing document.

## Discussion

Don’t call this method directly. SwiftUI calls it when you
call the [`openDocument`](/documentation/SwiftUI/EnvironmentValues/openDocument) action:

```
do {
    try await openDocument(at: url)
} catch {
    // Handle error
}
```

For information about how Swift uses the `callAsFunction()` method to
simplify call site syntax, see
[Methods with Special Names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#ID622)
in *The Swift Programming Language*.

---

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